1. Field of the Invention
The present invention relates to a geomagnetic sensor for computing an azimuth and a method thereof, and more particularly, to a geomagnetic sensor for compensating an azimuth and a method thereof, in which normalization factors are simply computed for compensation of the azimuth
2. Description of the Related Art
A geomagnetic sensor serves to sense the intensity of geomagnetism and its direction, which cannot be sensed by a human being. Particularly, a sensor that senses the geomagnetism using a fluxgate is called a fluxgate type geomagnetic sensor.
The fluxgate type geomagnetic sensor uses a material having high magnetic permeability, such as permalloy, as a magnetic core. The fluxgate type geomagnetic sensor generates an excited magnetic field through a driving coil that winds the magnetic core, and senses the size and the direction of an external magnetic field by sensing secondary high frequency components in proportion to the external magnetic field generated by magnetic saturation of the magnetic core and nonlinear magnetic characteristics.
Recently, with the increasing development of the micro electro mechanical system (MEMS) technology, it has come that a micromini fluxgate sensor of low power consumption can be fabricated using the MEMS technology and is used in cellular phones, PDAs, notebook computers, and various portable electronic devices.
Meanwhile, the geomagnetic sensor generally uses a two-axis or three-axis fluxgate. If the geomagnetic sensor is tilted when an azimuth is sensed using the geomagnetic sensor, the azimuth may be computed in error. To avoid such an error, an algorithm is generally performed, which compensates an azimuth using a tilt angle, i.e., a pitch angle or a roll angle. In a conventional geomagnetic sensor, operation of the pitch angle or the roll angle is performed using a two-axis acceleration sensor to compensate the azimuth.
The azimuth compensation work means that the azimuth is prevented from being distorted by the pitch angle or the roll angle. To perform the azimuth compensation work in a geomagnetic sensor provided with X, Y, and Z axis fluxgates, preparatory works are required. In other words, a maximum value and a minimum value from output values of the X and Z axis fluxgates are obtained as the output values of the X and Z axis fluxgates are monitored while the geomagnetic sensor is being swung at least one or more times around the Y axis. Then, operation of normalization factors is performed using the maximum value and the minimum value. The normalization factors mean those used for normalization that maps the output values of the X, Y and Z fluxgates onto values within a previously set range. Specifically, scale and offset values are used as the normalization factors.
If operation of the scale and offset values of the X and Z axes is performed, the operated values are stored in a memory of the geomagnetic sensor. Afterwards, a maximum value and a minimum value from output values of Y and Z axis fluxgates are obtained as the output values of the Y and Z axis fluxgates are monitored while the geomagnetic sensor is being swung at least one or more times around the X axis. Then, operation of normalization factors is performed using the maximum value and the minimum value.
The aforementioned conventional geomagnetic sensor has a problem in that the geomagnetic sensor is swung in various directions several times to perform the azimuth compensation work. For this reason, it is difficult to facilitate the azimuth compensation work.